In the mobile communication, device triggering is the means by which a server located outside a Mobile Operation Network indicates necessity of communication such that a terminal connects to the server. The device triggering has to be available both cases when the terminal is in the online state and has data connection and when the terminal is in the online state but has no data connection.
FIG. 1 is a diagram illustrating architecture of a mobile operator network interworking with a circuit network for providing Short Message Service (SMS), and FIG. 2 is a diagram illustrating a mobile communication network including the packet service network and an application server. Referring to FIGS. 1 and 2, the solution making it possible to fulfilling the requirements of the current device triggering is an SMS-based push service. That is, if the information on the external server through SMS, the terminal which receives the SMS establishes a Packet Data Network (PDN) connection to connect to the external server. However, the SMS-based connection method uses a Circuit Switched network, there is a problem in that the LTE system using only the Packet Switched (PS) network has to interwork with the legacy Circuit Switched network. There is therefore a need of a method for supporting device triggering only with the Packet Switched network without interworking with the Circuit Switched network.
The device triggering in the packet network may causes signaling overhead. That is, if several application servers located at external networks request for device trigger service to communicate small amount of data, this causes frequent state transitions of the terminal, resulting in signaling overhead of the mobile communication network. For example, if a terminal which has received a paging for device triggering of an application connects to an application server to exchanged small amount of data and enters the idle state and, afterward, if the paging for device triggering associated with another application server is received, the terminal transitions to the active state to exchange small amount of data and then transitions to the idle state, repeatedly. The signaling overhead problem is exemplified as shown in FIG. 3. FIG. 3 is a graph illustrating an exemplary signaling overhead increment caused by state transition. As shown in FIG. 3, the signaling overhead is the problem caused by the application server using notification for the data terminal (e.g. smartphone)